cgen: fix array.filter(anon_fn)

vlib/builtin/array_test.v

@@ -529,6 +529,21 @@ fn test_filter() {
 	//assert arr.filter(arr % 2).len == 5
 }
 
+fn test_anon_fn_filter() {
+	filter_num := fn (i int) bool {
+		return i % 2 == 0
+	}
+	assert [1,2,3,4,5].filter(filter_num) == [2,4]
+}
+
+fn test_anon_fn_arg_filter() {
+	a := [1,2,3,4].filter(fn (i int) bool {
+		return i % 2 == 0
+	})
+
+	assert a == [2,4]
+}
+
 fn map_test_helper_1(i int) int {
 	return i * i
 }

vlib/v/gen/cgen.v

@@ -3245,10 +3245,28 @@ fn (mut g Gen) gen_filter(node ast.CallExpr) {
 	match node.args[0].expr {
 		ast.Ident {
 			if it.kind == .function {
-				g.writeln('${node.args[0]}(it)')
+				g.write('${it.name}(it)')
+			} else if it.kind == .variable {
+				var_info := it.var_info()
+				sym_t := g.table.get_type_symbol(var_info.typ)
+				if sym_t.kind == .function {
+					g.write('${it.name}(it)')
 				} else {
 					g.expr(node.args[0].expr)
 				}
+			} else {
+				g.expr(node.args[0].expr)
+			}
+		}
+		ast.AnonFn {
+			pos := g.out.len
+			def_pos := g.definitions.len
+			g.stmt(it.decl)
+			fn_body := g.out.after(pos)
+			g.out.go_back(fn_body.len)
+			g.definitions.go_back(g.definitions.len - def_pos)
+			g.definitions.write(fn_body)
+			g.write('${it.decl.name}(it)')
 		}
 		else {
 			g.expr(node.args[0].expr)